Semiconductor devices have been produced by the steps of coating an inorganic substrate with a photoresist; patterning the photoresist film by exposure to light and subsequent development; etching exposed region of the inorganic substrate using the patterned photoresist film as a mask to form minute circuits; and removing the patterned photoresist film from the inorganic substrate. Alternatively, after forming minute circuits in the same manner as above, the patterned photoresist film is ashed, and then the remaining resist residues are removed from the inorganic substrate.
To strip photoresist (PR), UV/plasma hardened PR and plasma etch/ash residues, common organic solvents alone are generally not effective to provide required cleaning capability. Special active agents such as fluorides and alkaline bases are frequently used in microelectronic formulations. However, many bases such as amines and ammonium hydroxides will lead severe metal corrosion. Utilization of corrosion inhibitors may alleviate/minimize such metal corrosion, but generally can not provide enough protection for severe corrosion situations/formulations. Thus, working compositions need to be totally or “reasonably compatible” with metal without corrosion inhibitors. To meet modern microelectronic performance requirement, “reasonably compatible” is defined as “have metal etch rate of 20 Å/min or less”. “Totally compatible” is defined as “have metal etch rate of 8 Å/min or less”.
Microelectronic compositions at basic pH frequently encounter poor metal stack compatibility during wet PR stripping and subsequent water rinse processes. Galvanic corrosion of metal stacks poses even greater challenges. Utilization of corrosion inhibitors often result in surface modifications or leave residues on surface, leading to undesirable electric performance variations.
Among the many type of corrosion inhibitors suggested for use in such microelectronic cleaning compositions are azoles, particularly tetrazole and triazoles, and especially benzotriazole, and they have been employed at levels of 0.2 to 2% or more. Examples of cleaners with the mention of such azoles, especially benzotriazole, use as a corrosion inhibitor include, but are not limited to EP 1 178 359, EP 1,752,829, WO 2007/111694, US 2009/0170037, and WO 2007/044446. These cleaning compositions suggesting use of benzotriazole as a corrosion inhibitor are generally non-aqueous, organic solvent based cleaning compositions. But US 2003/144162 in paragraph [0042] indicates that benzotriazole does not prevent copper corrosion. However, although such triazoles appear to provide reasonably good copper protection from corrosion in some cases, generally in non-aqueous solvent based cleaner compositions, we have found that triazoles, such as benzotriazole, has a strong tendency to form a tightly bound polymer complex on the copper surfaces, which is believed to be a Cu ion/azole complex, such as Cu ion/benzotriazole complex, hereafter referred to as Cu (1)/azole and Cu (I)/BZT polymers, respectively. Such Cu (I)/azole polymer formation leads to detrimental effects if such polymer deposition is too thick or is not controlled. When benzotriazole is employed as a corrosion inhibitor the undesirable formation of such Cu(I)/BZT polymer is especially prevalent on copper surfaces and results in thick Cu(I)/BZT polymer especially when one of the major solvent components, dimethyl sulfoxide (DMSO), is employed in the cleaning compositions with benzotriazole. These Cu (I)/BZT polymers have been discovered to tightly bind to the copper surface and remain on the copper surface after typical water rinse processes employed following the stripping/cleaning process. Such problem has been found to be prevalent in substrates intended for flat panel displays.
Another class of metal, and especially copper or aluminum, corrosion inhibitors proposed for use in such cleaning compositions are polyhydroxylated phenol compounds containing vicinal hydroxyl groups, such as catechol, pyrogallol, and gallic acid. One disadvantage of the use of such polyhydroxylated phenol compounds as corrosion inhibitors is their tendency to bind tightly to silanols on the silicon wafers being cleaned. Such binding, even in small amounts modifies the silicon surface and causes degrading performances.
There is therefore a need for a microelectronics cleaning composition that can employ azole corrosion inhibitors that have no or minimized or inhibited Cu(I)/azole polymer formation. There is particularly a need for such cleaning composition that may be semi-aqueous and that does not produce significant metal corrosion even during the aqueous wash phase following cleaning of the substrates with the cleaning composition. An additional need is to have such compositions that are good performers for cleaning both aluminum and copper metallized microelectronic devices. A further need is to provide such cleaning compositions that inhibit binding of polyhydroxylated phenol compounds, employed as corrosion inhibitors, to silanols on the silicon wafers being cleaned and thereby inhibit surface modification of the microelectronic substrates by the polyhydroxylated phenol corrosion inhibitors.